Single-Leg Squat Performance and Its Relationship to Extensor Mechanism Strength After Anterior Cruciate Ligament Reconstruction.

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  • Additional Information
    • Source:
      Publisher: Sage Publications Country of Publication: United States NLM ID: 7609541 Publication Model: Print-Electronic Cited Medium: Internet ISSN: 1552-3365 (Electronic) Linking ISSN: 03635465 NLM ISO Abbreviation: Am J Sports Med Subsets: MEDLINE
    • Publication Information:
      Publication: 2004- : Thousand Oaks, CA : Sage Publications
      Original Publication: Baltimore, Williams & Wilkins.
    • Subject Terms:
      Anterior Cruciate Ligament Injuries/*surgery ; Anterior Cruciate Ligament Reconstruction/*rehabilitation ; Knee Injuries/*rehabilitation ; Knee Joint/*physiology ; Muscle Strength/*physiology; Adult ; Cohort Studies ; Exercise/physiology ; Female ; Hamstring Tendons/transplantation ; Humans ; Knee Injuries/surgery ; Knee Joint/surgery ; Male ; Prospective Studies ; Range of Motion, Articular ; Torque ; Transplantation, Autologous
    • Abstract:
      Background: Performance in strength and functional testing is important when considering return to sport after anterior cruciate ligament (ACL) reconstruction. Both knee extensor strength and the single-leg squat (SLS) have been used in this context.
      Purpose: To evaluate the relationship between knee extensor strength and SLS performance after primary ACL reconstruction.
      Study Design: Cohort study (Diagnosis); Level of evidence, 3.
      Methods: A prospective cohort of 100 patients was assessed 6 and 12 months after primary ACL reconstruction with a hamstring tendon autograft. Knee extensor peak torque was measured. Three sequential SLSs were performed, and the maximum flexion angle identified from frame-by-frame video analysis was used as the measure of squat performance. A limb symmetry index (LSI) was calculated and satisfactory performance defined as ≥90%.
      Results: Extensor mechanism strength deficits were seen in 75% of patients at 6 months and 57% at 12 months postoperatively. Mean extensor mechanism strength showed a large improvement between 6 and 12 months (123.6 vs 147.8 N·m, respectively; P < .001; Cohen d = 1.10), and while there was also a statistically significant improvement in the mean maximum flexion angle, the change was small (66.1° vs 68.1°, respectively; P = .011; Cohen d = 0.26). There was a weak positive correlation between knee extensor strength and the SLS maximum flexion angle at 6 months ( r = 0.342; P < .001) and 12 months ( r = 0.245; P = .014). An SLS LSI <90% was 80% specific and 35% sensitive for extensor mechanism weakness at 6 months and 79% specific and 18% sensitive at 12 months.
      Conclusion: Extensor mechanism strength deficits are common after ACL reconstruction but reduce between 6 and 12 months. The SLS maximum flexion angle has a weak linear relationship to knee extensor strength. SLS performance has high specificity but low sensitivity in identifying extensor mechanism strength deficits. The SLS maximum flexion angle is therefore a suboptimal surrogate test to identify extensor mechanism strength deficits as diagnosed by isokinetic dynamometric testing. However, unsatisfactory SLS performance indicates a very high chance of underlying extensor mechanism weakness.
    • Contributed Indexing:
      Keywords: ACL; extensor strength; rehabilitation; single-leg squat
    • Publication Date:
      Date Created: 20191022 Date Completed: 20200624 Latest Revision: 20200624
    • Publication Date:
      20221213
    • Accession Number:
      10.1177/0363546519878432
    • Accession Number:
      31633995